The 28-year-old defender returns after three years away from the club he joined as a young lad from Cardiff City.
“It’s great to be back,” Collins told West Ham TV.
“Obviously having been here before and coming back and seeing some of the same old faces is great.
“As soon as I knew the interest was there from West Ham I couldn’t wait to get down and sign. I had a great affinity with the club and the fans when I was here the first time and I enjoyed my time here so much last time that it wasn’t a hard decision to make, to be honest.
“I think everyone knew that I didn’t really want to leave when I did [in 2009] because I was enjoying my time here so much. I’ve come back and I’m a much better player this time around so I can’t wait to get cracking and show the fans that I am a better player and can put in the performances on the pitch.
“I’ve got so many good memories - getting into the FA Cup final in my first season and finishing so high [ninth] in the league and then the way we escaped relegation that year was one of my fondest memories in football. Hopefully I won’t have too many more memories like that!
“I just cannot wait to get back and show the fans what a better player I am now.”